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Jim Denzler
8th Nov 2002, 04:05 pm
I want to extrude a shape along a spiral. My problem is how to create the spiral?
Thanks

8th Nov 2002, 04:54 pm
Jim,

You won't realise how funny this question is unless you've been around here for a while. I'm definately going to do a tutorial on this one day.

Do you mean a SPIRAL or do you mean a HELIX. It's a common error but it does make all the difference.

Either way, it's not possible to create a true spiral or helix in AutoCAD but you can draw an approximation. This can be a really tedious process and so it is usually done with a LISP routine. You'll find such a routine for creating a helix at this topic, http://www.cadtutor.net/forum/viewtopic.php?t=74 I don't have one for a spiral to hand but there must be one about somewhere.

8th Nov 2002, 04:58 pm
Wow, that didn't take long - don't you just love Google.

Have fun and do let us know how you get on.

Mr T
8th Nov 2002, 10:51 pm
Spiral - SOLID Modelling

If it's a spiral as in a cylinderical tube that is like a spring. You draw it like it's manufactured.

A 3D polyline drawn about a 3d solid cylinder, with points drawn on the outside at intervals to SNAP onto.

I do this as a lesson with my school kidz after they have drawn a nut and bolt to create a thread type shape.

Helix - SURFACE Modelling

Similar to above draw a cylinder then points at intervals around the cylinder then a 3D polyline. Copy it and move it up a touch. Then copy
and scale up the 3D polyline so it's got a larger radius then the other two.
Then create a RULE surf (or TAB surf sorry can't remember which one).

Phew !

Anyway they both work. The second one was used by one of my kidz to show a car suspension spring.

Nick

11th Nov 2002, 10:46 am
Thanks for that Mr.T

I just had a quick look on the old message board and I came across this:

The truth is that it can't be done with perfect accuracy since, as you have discovered, you can't extrude along a 3D spline. However, you can extrude along a 3D Polyline. So, providing you can bear to draw a helix using a 3D polyline, it can be done. Obviously, you only have straight line segments to play with so it can never be perfect. It's the kind of thing that lisp routines are written for. In fact, AutoCAD R12 came with a bonus LISP file called 3dspiral.lsp but sadly it is not included with more recent AutoCADs. However...

you can find one here: http://www.spaug.org/LISP_Index99.Html

and this...

Think about how it works, Here is an example for you.
Set your 3d viewport to SE. Use default UCS.
Start pline at 0,0,0 enter, @100<0,10 enter, @100<90,10 enter, @100<180,10 enter, @100<270,10 enter, @100<0,10 enter, @100<90,10 enter, @100<180,10 enter, @100<270,10 enter,@100<0,10 enter, @100<90,10 enter, @100<180,10 enter, @100<270,10 enter, Press enter to complete the command. Notive how it looks.
You can now use the PEDIT command and SPLINE the helix
I hope it helps you out to try this little exercise.

and this...

You can find 3dspiral.lsp here:

...and if anyone knows any more good sources of 3D spiral/helix stuff, post it here and I'll try to pull it all together in a new tutorial.

Mr T
11th Nov 2002, 09:56 pm
You can also have it smoothly curve since it's possible to pedit and FIT a 3D polyline, to fit smoothly between given points eg tangents correct.

Cheers

I'll post up an image of a pupils 'Car Suspension wheel' with one.

Nick

PS 'Mr T' is really my 'Teacher' name

Mr T
11th Nov 2002, 10:14 pm
Aha !

The great spiral debate continues !

Anyway here is an article with a lisp to download free that draws
a similar object.

http://pointa.autodesk.com/local/enu/portal/Articles/article.jsp?articleId=15872

Enjoy

nick

12th Nov 2002, 10:53 am
OK

maybe I don't need to do a tutorial, it's all there on the pointa article noted in Nicks post. It also included a download of the original spiral.lsp routine shipped with older versions of AutoCAD.

Mr T
12th Nov 2002, 09:32 pm
Yes, no tutorial needed. But how about a tutorial to draw the trees and garden in your 'Lighting/Shadow Tutorial', coz I'll be starting one this week !

It may be interesting to see if we draw things differently or similar. I have moved away from 'surface first then solid' to Solid then add on the surfaces if I really have to.

Why ? well it's easier to edit and manipulate a solid I find.

Although my 'Advanced Higher Graphics Course' stipulates I teach all surfaces(regions) and Solids and their editing/manipulation.

Cheers

Nick

PS Like my wee climbing pic AVITAR ?

Orbit
9th Mar 2003, 04:16 pm
Mr. T

Do you have any idea where the site you mentionate it above http://pointa.autodesk.com/local/enu/portal/Articles/article.jsp?articleId=15872 is?

It looks to me like an index but remember it was a tutorial about a spiral few weeks ago.

robfowler
9th Mar 2003, 06:53 pm
Autodesk has recently rejigged its site and it now seems that saved links now return us to the home page!

I think some of the tips and tutorials have been removed, but I do hope that Autodesk reinstates them. I know that there is increasing pressure for them to do this as folks have got used to the extensive list of tips and tutorials that were there before.

Rob.

Orbit
9th Mar 2003, 07:29 pm
True Rob

I was searching all over that site and the only thing found it about spiral is

No tutorial, no further explanations, nada. I used the lisp and still missing something essential.

robfowler
9th Mar 2003, 07:41 pm
What is it you are trying to do?

Rob.

Orbit
9th Mar 2003, 08:54 pm
I am trying to do a spiral. I followed the lisp prog. but my spiral is flat and in the same plan.
I tried to change the UCS and exploded the spiral to give segments the wanted rotation angle. However, I cannot reach a content result.

robfowler
10th Mar 2003, 12:41 am
There are 2 spiral lisp routines kicking around that I know of. One is for a 2D spiral (sounds like the one you've got) and the other is for a 3D spiral (helix).

The last one is what you want. I have a copy and can email it to you if you post me your private email address.

Rob.

Raider
26th May 2005, 09:27 am
Can anybody tell me how to post a pic of a drill I did here in autocad? Im new to the forum. I did a helix, copy, rotate and extrude of a twist drill and it turned out ok, I wanted to post it for other people with the same question. I used the helix AutoLISP that member fuccaro had posted, many thanks to him for his help!

fuccaro
26th May 2005, 11:24 am
Welcome Raider!